1. Field of the Invention
This invention relates to a wheel rim, and more particularly to a lightweight wheel rim that is connected to spokes at two opposite sides thereof.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional bicycle wheel rim 1 disclosed in U.S. Pat. No. 6,402,256 is shown to include a pair of left and right side walls 11 (only one is shown in FIG. 1), and annular inner and outer walls 12, 13 interconnecting the left and right side walls 11 and spaced apart from each other along a radial direction of the wheel rim 1. The inner wall 12 has a middle portion that is formed with a plurality of alternately arranged mounting holes 121 and dented portions 122. A plurality of steel spokes 14 are locked respectively within the mounting holes 121 in the inner wall 12. The dented portions 122 are thinner than the portions of the inner wall 12 defining the mounting holes 121. The outer wall 13 cooperates with the left and right sidewalls 11 to define a tire-mounting space 15 for supporting a tire (not shown).
Although the total weight of the wheel rim 1 can be reduced due to formation of the dented portions 122, the mounting holes 121 and the dented portions 122 are disposed at the middle portion of the inner wall 12, thereby resulting in a considerable decrease in the strength of the inner wall 12. As such, the portions of the inner wall 12 that define the mounting holes 121 are likely to deform due to the pulling force of the spokes 14.